In recent years, a wireless communication system including a portable phone system is a significantly meaningful social infrastructure, and effect of stopping the operation of a service due to a failure is not small. Therefore, continuity and stability of services are taken into account in the development of the wireless communication system. The amount of data communication in portable phone services is increasing due to advanced functions of wireless terminals as well as diversification and sophistication of services in the wireless communication system.
One of the standards in a wireless communication method specified by 3GPP (3rd Generation Partnership Project) includes LTE (Long Term Evolution) released as 3GPP Release.8. In the LTE, a base station apparatus (called “eNode B”) is divided into a wireless unit and a control/baseband unit (also called “wireless control unit” or “baseband unit”) due to indoor installation, and the wireless unit and the control/baseband unit are connected by a communication interface. In the LTE, the wireless unit is called an RRH (Radio Remote Head), and the control/baseband processing unit is called a BBU (Base Band Unit). The BBU is also called “Radio Equipment Control (REC)” in some cases, and the RRH is also called “Radio Equipment (RE)” in some cases.
The BBU and the RRH are usually connected by CPRI (Common Public Radio Interface). The CPRI is one of BBU-RRH interfaces. When the CPRI is applied, a CPRI signal including a baseband signal (IQ data) and a maintenance monitoring signal is transmitted and received between the BBU and the RRH according to a CPRI protocol. In general, the RRH can be installed at a location several km away from the BBU through connection via an optical line (optical fiber) for transmitting and receiving the CPRI signal.
For more information, see National Publication of International Patent Application No. 2007-529926, Japanese Patent Laid-Open No. 2011-171961, International Publication No. WO2008/114351, International Publication No. 2010/044142, and Japanese Patent Laid-Open No. 2011-130179.
Usually, a plurality of RRHs are connected to one BBU, and a plurality of cells or sectors are operated. When the CPRI is used to connect the BBU and the RRHs, a layer 2 and higher layers are terminated between the BBU and the RRHs in the CPRI protocol for connecting the BBU and the RRHs. Therefore, when the connection relationship between the BBU and the RRHs is changed, the setting or physical connection of all paths between the BBU and the RRHs is changed.